Analyzing Operative Outcomes for Proximal Aortic Replacement

Morbidity and mortality from proximal aortic replacement remain high when compared with other surgical procedures, but research indicates that patient outcomes have improved over the last 30 years. Much of this has been attributed to advances in operative approaches, perioperative care, and increased surveillance. For patients undergoing these procedures, better character­izing outcomes and determin­ing predictors of mortality and major morbidity are important for clinicians managing this patient population.

In the Journal of the American College of Cardiology, G. Chad Hughes, MD, and colleagues had an analysis published that looked at operative outcomes for ascending aorta and arch replacement on a national scale. The study also reviewed risk factors for postoperative mortality and major morbidity. “Our study provides a broad overview of the current practices and outcomes for proximal aortic replacement in North America,” says Dr. Hughes. “With more than 45,000 patients from the Society of Thoracic Surgeons Database involved in our analysis, we have the largest cohort of proximal aortic replacements that have been reported to date.”

Examining Outcomes for Proximal Aortic Replacement

In the study by Dr. Hughes and colleagues, roughly 60% of proximal aortic replacement cases were elective, 20% were urgent, and 20% were emergent. From 2004 to 2009, the number of centers that reported performing aortic replacement, as well as the overall number of patients treated, increased dramatically, although the average number of patients treated per center remained relatively constant. In 2004, 285 centers in North America treated 2,121 patients. In 2008, there were 806 centers that treated 11,033 patients. “Outcomes were excellent for elective proximal aortic replacement but sharply deteriorated when the procedure was done urgently,” Dr. Hughes says (Figure). The elective mortality was 3.5%, but the overall operative mortality rate was 8.3%, and the stroke rate was 6.6%.

While it was not surprising that emergency procedures would result in worse outcomes, Dr. Hughes says his study group’s findings are still helpful for clinicians because they provide new and valuable information with regard to the “real world” outcomes of these pro­cedures, which had not been previously known out­side of reports from select high-volume expert centers. “Furthermore, given the significantly improved out­comes in the elective situation, the findings suggest that increased screening of at-risk populations and lowering aortic diameter thresholds that trigger elec­tive intervention could improve outcomes by reducing the number of operations performed in non-elective circumstances.” Finally, outcomes associated with type A dissection repair remain suboptimal, a find­ing that highlights the need for greater improvement efforts when managing these non-elective patients.

Predicting Operative Mortality

Dr. Hughes’s study also developed a risk model for predicting mortality and major morbidity in proximal aortic replacement. When compared with elective surgery, patients were twice as likely to die after urgent surgery and nearly six times as likely to die after emergent surgery (Table). “These findings confirm the critical prognostic importance of procedure status,” says Dr. Hughes. “Our predictive model may help clinicians in the development of risk stratification strategies when they counsel patients.”

Performance of concurrent CABG or mitral valve procedures was shown to increase risk for mortality and major morbidity among the overall study cohort. In addition, concomitant arch replacement was linked to a higher risk for adverse outcomes in all models, but root replacement was not. Adverse outcomes were more common after supracoronary ascending replacement in both elective and non-elective settings. This was likely secondary to the older age and greater comorbidities of these patients. Among elective patients, end-stage renal disease and reoperative status were the strongest predictors of mortality.

Opportunity Knocks Before Elective Aortic Surgery

“For clinicians counseling patients before an elective proximal aortic replacement procedure, our predictive model provides a guide to estimating the risk of perioperative death and major morbidity in the setting of renal or lung disease, heart failure, and other comorbidities,” Dr. Hughes says. “By examining the role of volume and other processes of care in thoracic aortic surgery, we have an opportunity to optimize the quality of care for patients in need of proximal aortic replacement.”

Current risk-benefit estimates for recommending elective proximal aortic replacement in published guidelines are based upon a predicted operative mortality of 5.0%. “With the low overall mortality rates we observed in elective proximal aortic replacement, the question arises as to whether we’re waiting too long to intervene,” explains Dr. Hughes. “The diameter threshold could be lowered the next time the guidelines for aortic replacement are written. In the meantime, more practical approaches are to increase our screening efforts and improve medical therapy for patients at risk for aortic aneurysm or dissection. Continuing to broaden our clinical awareness of thoracic aneurysms and dissections is important to reducing the need for urgent or emergent operations. It could also reduce the procedural morbidity and mortality associated with proximal aortic replacement.”